Locks are commonly used to retain doors or windows or the like in either an open or closed condition. In the case where it is desirable control the lock from a remote location, an electrically operated lock may be used. One form of electrically operated lock is an electromagnetic lock. These typically comprise an armature of ferrous material and an electromagnet. Activation of the electromagnet causes strong magnetic attraction between the armature and electromagnet. It is necessary for current to flow through the electromagnet to maintain the attraction. Deactivation of the electromagnet allows the armature to release from the electromagnet.
In the case of security doors in commercial premises or the like, electromagnetic locks are sometimes used which require a force of about 2000N to 5000N to break the attraction between the armature and the electromagnet. In order to provide such strong magnetic attraction it is necessary to use a strong electromagnet and a correspondingly large armature. In addition, a current of approximately between 40 mA up to 400 mA must constantly flow through the electromagnet whilst it is retaining the door.
The following formula shows the general equation determining the electromagnet holding force:F=K*(Bg)2*A Where
F is the holding force in Newton,
K is the constant,
Bg is full density of magnetism (Wbm2)
A is the surface area of the electromagnet (m2)
It would be advantageous to provide a remotely operable lock with an adequately strong locking action which uses either a smaller amount of raw materials during construction or which uses less electricity during operation than existing locks.